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1.
Tech Coloproctol ; 28(1): 23, 2024 01 10.
Article in English | MEDLINE | ID: mdl-38198036

ABSTRACT

In France, about 2000 new cases of anal cancer are diagnosed annually. Squamous cell carcinoma is the most common histological type, mostly occurring secondary to persistent HPV16 infection. Invasive cancer is preceded by precancerous lesions. In addition to patients with a personal history of precancerous lesions and anal cancer, three groups are at very high risk of anal cancer: (i) men who have sex with men and are living with HIV, (ii) women with a history of high-grade squamous intraepithelial lesions (HSILs) or vulvar HPV cancer, and (iii) women who received a solid organ transplant more than 10 years ago. The purpose of screening is to detect HSILs so that they can be treated, thereby reducing the risk of progression to cancer. All patients with symptoms should undergo a proctological examination including standard anoscopy. For asymptomatic patients at risk, an initial HPV16 test makes it possible to target patients at risk of HSILs likely to progress to cancer. Anal cytology is a sensitive test for HSIL detection. Its sensitivity is greater than 80% and exceeds that of proctological examination with standard anoscopy. It is indicated in the event of a positive HPV16 test. In the presence of cytological abnormalities and/or lesions and a suspicion of dysplasia on clinical examination, high-resolution anoscopy is indicated. Performance is superior to that of proctological examination with standard anoscopy. However, this technique is not widely available, which limits its use. If high-resolution anoscopy is not possible, screening by a standard proctological examination is an alternative. There is a need to develop high-resolution anoscopy and triage tests and to evaluate screening strategies.


Subject(s)
Anus Neoplasms , Precancerous Conditions , Sexual and Gender Minorities , Male , Humans , Female , Human Papillomavirus Viruses , Homosexuality, Male , Precancerous Conditions/diagnosis , Anus Neoplasms/diagnosis
2.
Ann Pharm Fr ; 79(6): 609-616, 2021 Nov.
Article in French | MEDLINE | ID: mdl-33961828

ABSTRACT

Hybrid medicines are defined as medicines that do not fill generic medicines' definition, forming a medicines group that stands half-way between reference medicinal products and generic medicines. The term "hybrid" was introduced in France in 2018, but the concept has existed for some fifteen years in Community legislation. The aim of this work is to expose hybrid medicines' legal framework, in Europe and in France. Hybrid medicines' European legal framework specifies in a guide of the European Medicines Agency, marketing authorization procedures that can be used for hybrid medicines, and what is required for marketing authorization applications. In France, a register of hybrid medicines' groups has been created, and registration procedures were specified in a decree at the end of 2019. Legal texts also underlined that substitution within hybrid medicines' group would be possible for some specific medical cases. Decrees specifying hybrid medicines' groups list and specific medical cases allowing substitution, are not appeared yet at the end of February 2021. Moreover, some elements have never been raised, particularly medical and economic assessment modalities.


Subject(s)
Drugs, Generic , Marketing , Europe , France
3.
Ann Pharm Fr ; 79(6): 664-689, 2021 Nov.
Article in French | MEDLINE | ID: mdl-33887249

ABSTRACT

OBJECTIVES: The aim of this study is to give an overview of hybrid medicines, term introduced in France by the Social Security Financing Act for 2019, with special attention to those available in Paris Public Hospitals (AP-HP), and to analyze their therapeutic values and economic issues. METHODS: Research by keywords on European and French health authorities' websites was done to provide a list of hybrid medicines. Then, an analysis of their profile and of their differences from reference medicinal products was done. A reflection on hybrid medicines likeness to "new medicines" or to "generic medicines" was carried out. Lastly, their therapeutic interests, their risks and their costs were assessed. RESULTS: In France 85 hybrid medicines were identified, including 41 commercialized, and 21 available in AP-HP. Six different types of differences from the reference medicinal product were found out. Over 90% of hybrid medicines show at least one interest compared to the reference medicines, even if it is not a major innovation. However, more than a third of hybrid medicines are associated to a risk in case of drug substitution with the reference medicinal product. Hybrid medicines costs appear to be lower than reference medicines, but with smaller discounts than what is usually observed with generic medicines. CONCLUSION: Hybrid medicines constitute a very heterogeneous population, whether in terms of differences from reference medicines, of interests or risks. Common rules development for all hybrid medicines may be complex and would require taking every couple hybrid/reference medicines specificities into account.


Subject(s)
Drugs, Generic , Hospitals, Public , France , Paris
4.
J Appl Toxicol ; 37(3): 287-295, 2017 03.
Article in English | MEDLINE | ID: mdl-27440042

ABSTRACT

The lack of a reliable in vitro system to assess reprotoxicity is an emerging problem in the context of European law for Registration, Evaluation, Authorization and Restriction of Chemicals (REACH, 2007), as it requires a reduction in animal utilization for testing. Furthermore, in vitro reprotoxicological tests would be more relevant and greatly improved by integrating both hepatic metabolism and the blood-testis barrier. Here, we took advantage of an integrated insert in a dynamic microfluidic platform (IIDMP) to co-cultivate hepatocytes in biochip and Sertoli cells in the bicameral chamber. This microfluidic tool has been previously demonstrated to be helpful in cell function and/or quality improvement. We demonstrate that permeability of the Sertoli barrier is reduced by dynamic coculture in our system. Exometabolomics analysis reveals that interactions between hepatocytes and Sertoli cells may have been mediated by the polyamines increase and/or mid-chain fatty acid decrease in the circulating medium. These metabolic changes may be involved in permeability reduction by contributing to modifying junction protein quantity and localization. The present study gives an example of IIDMP as an in vitro partitioning/transport model for cell culture and toxicological testing. Further, based on both our previous results using an intestinal-hepatic cell coculture and the present study, IIDMP seems to be well-suited for (i) assessing the dose-response effect of chemicals within the rodent or human male reproductive tract, and (ii) improving the quality of reprotoxicological assays by including hepatic metabolism. Copyright © 2016 John Wiley & Sons, Ltd.


Subject(s)
Blood-Testis Barrier , Hepatocytes/drug effects , Sertoli Cells/drug effects , Tight Junctions/drug effects , Animal Use Alternatives , Animals , Bioreactors , Coculture Techniques , Hepatocytes/cytology , Hepatocytes/metabolism , Male , Microfluidics , Permeability , Rats , Rats, Sprague-Dawley , Sertoli Cells/cytology , Sertoli Cells/metabolism , Tight Junctions/metabolism
5.
Org Biomol Chem ; 13(27): 7351-80, 2015 Jul 21.
Article in English | MEDLINE | ID: mdl-26077713

ABSTRACT

Thanks to the beneficial effect of fluorine substitution on the pharmacokinetic properties of molecules, an ever increasing number of marketed drugs incorporate a fluorine atom into their structure. As a consequence, the synthesis of fluorinated molecules has become a very active research field. Among the numerous approaches, fluorinated enol ethers are valuable building blocks that allow the introduction of a fluoro- or difluoromethyl group through a wide variety of reactions. The present review lists different methods for their preparation and sums up their numerous synthetic applications.

6.
Phys Chem Chem Phys ; 17(14): 8740-9, 2015 Apr 14.
Article in English | MEDLINE | ID: mdl-25739103

ABSTRACT

Conception of new pyrimidylmethylamine (pyrma) ligands and their corresponding Pd(II) complexes has been described. Both symmetrical and non-symmetrical ligands were prepared and subjected to complexation. Two different coordination modes, Pd(N,N)- or Pd(C,N,N)-pyrma, have been evidenced depending on the substitution of the pyrimidine ring and the nature or the shape of the additional pendant arm. In a non-symmetrical pyrimidine series, the substituent-induced discrimination of each heterocyclic nitrogen atom provoked regio-controlled coordination to the metal center. The molecular structure of pyrma-Pd(II) complexes in the solution state has been elucidated thanks to combined NMR experiments and DFT calculations. This study highlights the potency of (15)N and (13)C NMR spectroscopy for the elucidation of the regio-selective coordination to the Pd(II) in the pyrma-based complex series. DFT calculations were highly relevant to the identification of crucial factors that govern the regio-selectivity and the complexation modes. Close predicted and experimental chemical shift values put into relief the reliability of coordination modes for the most stable complexes in solution, depicted by DFT approaches.

7.
Toxicol In Vitro ; 29(4): 803-12, 2015 Jun.
Article in English | MEDLINE | ID: mdl-25765475

ABSTRACT

In vitro metabolism of permethrin, a pyrethroid insecticide, was assessed in primary human hepatocytes. In vitro kinetic experiments were performed to estimate the Michaelis-Menten parameters and the clearances or formation rates of the permethrin isomers (cis- and trans-) and three metabolites, cis- and trans-3-(2,2 dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (cis- and trans-DCCA) and 3-phenoxybenzoic acid (3-PBA). Non-specific binding and the activity of the enzymes involved in permethrin's metabolism (cytochromes P450 and carboxylesterases) were quantified. Trans-permethrin was cleared more rapidly than cis-permethrin with a 2.6-factor (25.7±0.6 and 10.1±0.3 µL/min/10(6) cells respectively). A 3-factor was observed between the formation rates of DCCA and 3-PBA obtained from trans- and cis-permethrin. For both isomers, the rate of formation of DCCA was higher than the one of 3-PBA. The metabolism of the isomers in mixture was also quantified. The co-incubation of isomers at different ratios showed the low inhibitory potential of cis- and trans-permethrin on each other. The estimates of the clearances and the formation rates in the co-incubation condition did not differ from the estimates obtained with a separate incubation. These metabolic parameters may be integrated in physiologically based pharmacokinetic (PBPK) models to predict the fate of permethrin and metabolites in the human body.


Subject(s)
Hepatocytes/metabolism , Insecticides/metabolism , Permethrin/metabolism , Biotransformation , Cryopreservation , Cytochrome P-450 Enzyme System/metabolism , Esterases/metabolism , Female , Humans , Insecticides/chemistry , Isomerism , Male , Models, Statistical , Permethrin/chemistry , Primary Cell Culture , Toxicokinetics
8.
Br J Dermatol ; 169(6): 1322-5, 2013 Dec.
Article in English | MEDLINE | ID: mdl-23957618

ABSTRACT

BACKGROUND: Peeling skin disease (PSD), a generalized inflammatory form of peeling skin syndrome, is caused by autosomal recessive nonsense mutations in the corneodesmosin gene (CDSN). OBJECTIVES: To investigate a novel mutation in CDSN. METHODS: A 50-year-old white woman showed widespread peeling with erythema and elevated serum IgE. DNA sequencing, immunohistochemistry, Western blot and real-time polymerase chain reaction analyses of skin biopsies were performed in order to study the genetics and to characterize the molecular profile of the disease. RESULTS: Histology showed hyperkeratosis and acanthosis of the epidermis, and inflammatory infiltrates in the dermis. DNA sequencing revealed a homozygous mutation leading to a premature termination codon in CDSN: p.Gly142*. Protein analyses showed reduced expression of a 16-kDa corneodesmosin mutant in the upper epidermal layers, whereas the full-length protein was absent. CONCLUSIONS: These results are interesting regarding the genotype-phenotype correlations in diseases caused by CDSN mutations. The PSD-causing CDSN mutations identified heretofore result in total corneodesmosin loss, suggesting that PSD is due to full corneodesmosin deficiency. Here, we show for the first time that a mutant corneodesmosin can be stably expressed in some patients with PSD, and that this truncated protein is very probably nonfunctional.


Subject(s)
Codon, Nonsense/genetics , Dermatitis, Exfoliative/genetics , Glycoproteins/genetics , Skin Diseases, Genetic/genetics , Female , Homozygote , Humans , Intercellular Signaling Peptides and Proteins , Middle Aged
9.
Article in English | MEDLINE | ID: mdl-23848773

ABSTRACT

A microfluidic method is presented to measure the elastic membrane properties of a population of microcapsules with diameter of order 60 µm. The technique consists of flowing a suspension of capsules enclosed by a polymerized ovalbumin membrane through a square-section microfluidic channel with cross dimension comparable with the capsule mean diameter. The deformed profile and the velocity of a given capsule are recorded. A full mechanical model of the motion and deformation of an initially spherical capsule flowing inside a square-section channel is designed for different flow strengths, confinement ratios, and membrane constitutive laws. The experimental deformed profiles are analyzed with the numerical model. This allows us to find the ratio between the viscous and elastic forces and thus the shear elastic modulus of the membrane. We show that the ovalbumin membrane tends to have a strain-softening behavior under the conditions studied here.


Subject(s)
Capsules , Membranes, Artificial , Microfluidics/methods , Models, Chemical , Models, Molecular , Ovalbumin/chemistry , Computer Simulation
10.
J Environ Radioact ; 121: 43-54, 2013 Jul.
Article in English | MEDLINE | ID: mdl-22608977

ABSTRACT

Apart from radiocaesium and radiostrontium, there have been few studies on the foliar transfer of radionuclides in plants. Consequently, specific translocation factor (ftr) values for (129)I, (79)Se and (36)Cl are still missing from the IAEA reference databases. The translocation of short - lived isotopes, (125)I and (75)Se, and of (36)Cl to wheat grain were measured under field conditions following acute and chronic wet foliar contamination at various plant growth stages in the absence of leaching caused by rain. The translocation factors ranged from 0.02% to 1.1% for (125)I (a value similar to Sr), from 0.1% to 16.5% for (75)Se, and from 1% to 14.9% for (36)Cl. Both (36)Cl and (75)Se were as mobile as Cs. The phenomenological analysis showed that each element displayed a specific behavior. Iodide showed the lowest apparent mobility because of its preferential fixation in or on the leaves and a significant amount probably volatilized. Selenite internal transfer was significant and possibly utilized the sulphur metabolic pathway. However bio - methylation of selenite may have led to increased volatilization. Chloride was very mobile and quickly diffused throughout the plant. In addition, the analysis underlined the importance of plant growth responses to annual variations in weather conditions that can affect open field experiments because plant growth stage played a major role in ftr values dispersion. The chronic contamination results suggested that a series of acute contamination events had an additive effect on translocated elements. The highest translocation value obtained for an acute contamination event was shown to be a good conservative assessment of chronic contamination if data on chronic contamination translocation are lacking. The absence of rain leaching during the experiment meant that this investigation avoided potential radionuclide transfer by the roots, which also meant that radionuclide retention on or in the leaves was maximized. This study was therefore able to obtain accurate translocation factors, which are probably among the highest that could be recorded.


Subject(s)
Chlorine/pharmacokinetics , Iodides/pharmacokinetics , Plant Leaves/radiation effects , Radioisotopes/pharmacokinetics , Seeds/radiation effects , Selenious Acid/pharmacokinetics , Triticum/radiation effects , Biological Transport/radiation effects , Food Contamination, Radioactive , Iodine Radioisotopes/pharmacokinetics , Plant Leaves/metabolism , Radioactive Pollutants/pharmacokinetics , Rain , Seeds/metabolism , Selenium Radioisotopes/pharmacokinetics , Triticum/growth & development , Triticum/metabolism
13.
J Colloid Interface Sci ; 355(1): 81-8, 2011 Mar 01.
Article in English | MEDLINE | ID: mdl-21194705

ABSTRACT

An inverse method is used to characterize the membrane mechanical behavior of liquid filled microcapsules. Cross-linked ovalbumin microcapsules are flowed and deformed into a cylindrical microchannel of comparable size. The deformed shape is compared to predictions obtained numerically when modeling a capsule under the same flow conditions. The unknown shear modulus value corresponds to the best fit. The degree of reticulation is estimated in parallel by determining the free amino groups remaining on the microcapsules after the cross-linking reaction. We characterize microcapsule populations fabricated at different reaction pH (5-8) and times (5-30 min) to study different cross-linking degrees. The capsule shear modulus and the amino groups are nearly constant with the reaction pH for the capsules fabricated after 5 min of reticulation. The shear modulus increases with the reaction time, while the NH(2) content decreases with it. A global increase in shear modulus with pH is also observed, together with an unexpected increase in NH(2) content. The study shows that the inverse method is capable of discriminating between various cross-linking degrees of microcapsules. Moreover, for this type of microcapsules, the mechanical method appears more reliable than the chemical one to obtain an estimation of their cross-linking degree.


Subject(s)
Membranes, Artificial , Ovalbumin/chemistry , Suspensions/chemistry , Cross-Linking Reagents/chemistry , Elastic Modulus , Hydrogen-Ion Concentration , Models, Theoretical , Particle Size , Surface Properties
14.
J Environ Radioact ; 100(9): 683-9, 2009 Sep.
Article in English | MEDLINE | ID: mdl-19019504

ABSTRACT

A review of the published literature about foliar transfer radionuclides to cereal grains was carried out with a special interest for translocation factors. Translocation describes the distribution of radionuclides within the plant after foliar deposition and radionuclide absorption onto the surface of leaves. It mainly depends on elements and the plant growth stage. The collected data were derived from both in-field and greenhouse experiments. They were analysed in order to select those coming from a contamination simulating a sprinkling irrigation or a rain. The data set contains 307 values. For each radionuclide the translocation factor values were sorted according to 5 characteristic stages of the cereal vegetative cycle: leaf development-tillering, stem elongation, earing-flowering, grain growth and ripening. Wheat, barley and rye have been treated together, independently of rice. For mobile elements such as cesium, the translocation factor is maximum when the contamination occurred at the earing-flowering stage. For less mobile elements such as strontium this maximum occurred for a foliar contamination at the grain growth stage. This review enabled us to propose the most probable value as well as the range of variation of translocation factors for some radionuclides according to the cereal vegetative cycle. Moreover, from these results, a radionuclide classification is proposed according to three mobility groups.


Subject(s)
Edible Grain/metabolism , Plant Leaves/metabolism , Radioisotopes/metabolism , Cesium Radioisotopes/metabolism , Hordeum/metabolism , Secale/metabolism , Strontium Radioisotopes/metabolism , Triticum/metabolism
15.
J Environ Radioact ; 97(2-3): 189-205, 2007.
Article in English | MEDLINE | ID: mdl-17574315

ABSTRACT

This study aimed to (i) evaluate whether the K(d) value of selenium is dependent upon the soil microbial activity and (ii) define the limitation of the use of the K(d) concept to describe selenium behaviour in soils when assessing the long-term radiological waste disposal risk. K(d) coefficients, as well as information on selenite speciation in the soil-solution, were derived from short- and long-term batch experiments with a calcareous silty clay soil in various microbial states. Soil microbial activity induced (i) an increase of the K(d) value from 16 l kg(-1) in sterile conditions to 130 l kg(-1) when the soil was amended with glucose and nitrate, and (ii) changes in selenium speciation both in the solution (presence of seleno-species other than free Se(IV)) and in the solid phase (Se linked to microorganisms). Although the K(d) coefficient adequately reflects the initial fractionation between soil-solid and soil-solution, it does not allow for speciation and microbial processes, which could affect reversibility, mobility and the long-term accumulation and uptake into crops.


Subject(s)
Selenium/metabolism , Soil Microbiology , Acetates/metabolism , Adsorption , Glucose/metabolism , Nitrates/metabolism , Sodium Selenite/chemistry , Sodium Selenite/metabolism
16.
Arch Virol ; 151(11): 2103-9, 2006 Nov.
Article in English | MEDLINE | ID: mdl-16791441

ABSTRACT

Prion diseases are caused by misfolding of the cellular prion protein, PrPC. In vitro studies have shown that PrP binds copper via the octarepeat region lying within the unstructured N-terminal segment of the protein, but the significance of copper in PrP metabolism remains unclear. Here, six specific antibodies recognizing different epitope regions of PrP were used to measure the effect of copper on the conformation of the molecule at the cell surface. Binding of an antibody, E149, to an epitope within the octarepeat domain of PrP is halved in the presence of copper, whereas binding of antibodies recognizing epitope motifs C-terminal to residue 90 of PrP remain relatively unaltered under equivalent conditions. These experiments strongly suggest that copper induces localized conformational change within the N-terminal portion of cell-surface PrPC.


Subject(s)
Copper/pharmacology , PrPC Proteins/chemistry , PrPC Proteins/drug effects , Protein Conformation/drug effects , Amino Acid Sequence , Animals , Antibodies, Monoclonal/immunology , Antibodies, Monoclonal/metabolism , CHO Cells , Cricetinae , Epitope Mapping , Epitopes , Immunoglobulin Fab Fragments/immunology , Immunoglobulin Fab Fragments/metabolism , Molecular Sequence Data , PrPC Proteins/metabolism
17.
Biomaterials ; 27(4): 586-95, 2006 Feb.
Article in English | MEDLINE | ID: mdl-16026825

ABSTRACT

Bone tissue engineering consists of culturing osteoblastic cells onto synthetic three-dimensional (3D) porous scaffolds. The organization of bone cells into 3D scaffolds is crucial for ex vivo tissue formation. Diffusional rates of nutrients could be greatly improved by perfusing media through the 3D microporous scaffolds. However, bone cells cultured in vitro are responsive to a variety of different mechanical signals including fluid flow and shear stresses. In this work, we attempt to study osteoblastic cells behaviour cultured within microdevices allowing continuous and homogenous feeding of cells. We have fabricated polydimethylsiloxane PDMS microdevices with a 3D microstructured channel network. Mouse calvarial osteoblastic cells MC3T3-E1 were seeded at 2x10(6)cells/ml and cultured into the microdevices under flow rates of 0, 5, 35 microl/min. Cells attached and proliferated well in the designed microdevices. Cell viability was found around 85% up to 1 to 2 weeks for shear stress value under 5 mPa. The alkaline phosphatase (ALP) activity was enhanced 3- and 7.5-fold inside the microdevices under static and dynamic flow of 5 microl/min as compared to flat static cultures in PDMS coated Petri dishes. Therefore, osteoblastic cells could be successfully cultured inside the microdevices under dynamic conditions and their ALP activity was enhanced. These results are promising for bone cell growth and differentiation as well as future tissue regeneration using larger 3D microfluidic microdevices.


Subject(s)
Bioreactors , Cell Culture Techniques/instrumentation , Mechanotransduction, Cellular/physiology , Microfluidics/instrumentation , Osteoblasts/cytology , Osteoblasts/physiology , Tissue Engineering/instrumentation , 3T3 Cells , Animals , Cell Culture Techniques/methods , Cell Proliferation , Cell Size , Cell Survival , Equipment Design , Equipment Failure Analysis , Mice , Microfluidics/methods , Tissue Engineering/methods
18.
Biomaterials ; 25(19): 4683-90, 2004 Aug.
Article in English | MEDLINE | ID: mdl-15120514

ABSTRACT

Combining the MEMS technology and biology requirements for tissue engineering, the fabrication processes of microstructured chambers and microchannels made in biodegradable photosensitive polymers are presented. The fabrication processes, based on softlithography are very fast and flexible. Various single and multistepwise microstructures could be achieved using the biodegradable polymers. Microstructures down to 50microm, which are suitable for liver reconstructs, could be fabricated. As the pCLLA acrylate photosensitive polymer has interesting property for implantable bioreactors, that is, its softness, we examined the ability of various mammalian cells to grow and spread on it. With Hep G2 cells, human umbilical blood vessel endothelial cells (HUVEC), 3T3-L1 mouse fibroblasts, static cultures could be successfully performed on single stepwise microstructures. Then, by using this photosensitive biodegradable polymer, a microstructure with simple fluidic channels is fabricated and a perfusion experiment could be carried out. Both cell cultures and perfusion experiments suggested the possibility to use the present photosensitive polymer as microfluidic supports for biodegradable bioreactors for implantation applications.


Subject(s)
Biocompatible Materials/chemistry , Cell Culture Techniques/methods , Cellobiose/analogs & derivatives , Endothelial Cells/cytology , Hepatoblastoma/pathology , Microfluidics/methods , Polymers/chemistry , Tissue Engineering/methods , 3T3-L1 Cells , Absorbable Implants , Animals , Biocompatible Materials/radiation effects , Cell Division , Cell Line, Tumor , Cell Survival , Equipment Design/methods , Humans , Liver Neoplasms/pathology , Materials Testing , Mice , Miniaturization/methods , Photochemistry/methods
19.
Biochemistry ; 41(36): 11017-24, 2002 Sep 10.
Article in English | MEDLINE | ID: mdl-12206674

ABSTRACT

The unfolding of cellular prion protein and its refolding to the scrapie isoform are related to prion diseases. Studies in the literature have shown that structures of proteins, either acidic or basic, are stabilized against denaturation by certain neutral salts, for example, sulfate and fluoride. Contrary to these observations, the full-length recombinant prion protein (amino acid residues 23-231) is denatured by these protein structure stabilizing salts. Under identical concentrations of salts, the structure of the sheep prion protein, which contains a greater number of glycine groups in the N-terminal unstructured segment than the mouse protein, becomes more destabilized. In contrast to the full-length protein, the C-terminal 121-231 prion protein fragment, consisting of all the structural elements of the protein, viz., three alpha-helices and two short beta-strands, is stabilized against denaturation by these salts. We suggest that an increase in the concentration of the anions on the surface of the prion protein molecule due to their preferential interaction with the glycine residues in the N-terminal segment destabilizes the structure of the prion protein by perturbing the prion helix 1 which is the most soluble of all the protein alpha-helices reported so far in the literature. The present results could be relevant to explain the observed structural conversion of the prion protein by anionic nucleic acids and sulfated glycosaminoglycans.


Subject(s)
Prions/chemistry , Protein Folding , Salts/chemistry , Amino Acid Sequence , Animals , Buffers , Circular Dichroism , Hot Temperature , Hydrogen-Ion Concentration , Mice , Molecular Sequence Data , Muramidase/chemistry , Peptide Fragments/chemistry , Protein Denaturation , Protein Structure, Secondary , Sheep , Solutions , Spectrometry, Fluorescence , Sulfates/chemistry , Tryptophan/chemistry
20.
J Mol Biol ; 322(1): 153-61, 2002 Sep 06.
Article in English | MEDLINE | ID: mdl-12215421

ABSTRACT

The full-length mouse recombinant prion protein (23-231 amino acid residues) contains all of its structural elements viz. three alpha-helices and a short two-stranded antiparallel beta-sheet in its C-terminal fragment comprising 121-231 amino acid residues. The incubated mixture of this prion protein fragment and nucleic acid results in the formation of amyloid fibres evidenced from electron microscopy, birefringence and fluorescence of the fibre bound Congo Red and Thioflavin T dyes, respectively. The secondary structure of the amyloid formed in nucleic acid solution is similar to the in vivo isolated prion protein 27-30 amyloid but unlike in it, a hydrophobic milieu is absent in the 121-231 amyloid. Thermal denaturation study demonstrates a partial unfolding of the protein fragment in nucleic acid solution. We propose that nucleic acid catalyses unfolding of prion protein helix 1 followed by a nucleation-dependent polymerisation of the protein to amyloid.


Subject(s)
Amyloid/chemistry , Amyloid/metabolism , DNA/pharmacology , Peptide Fragments/chemistry , Peptide Fragments/metabolism , Prions/chemistry , Prions/metabolism , Protein Folding , Amyloid/ultrastructure , Anilino Naphthalenesulfonates/metabolism , Animals , Benzothiazoles , Biopolymers/chemistry , Biopolymers/metabolism , Birefringence , Circular Dichroism , Congo Red/metabolism , Fluorescence , Hydrophobic and Hydrophilic Interactions , Mice , Microscopy, Electron , Peptide Fragments/ultrastructure , Prions/ultrastructure , Protein Binding , Protein Denaturation/drug effects , Protein Structure, Secondary/drug effects , Spectrometry, Fluorescence , Temperature , Thiazoles/metabolism , Tryptophan/metabolism
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